American composer Philip Glass says it was time to revisit his groundbreaking opera Einstein on the Beach, which is being mounted at the Luminato Festival in Toronto beginning Friday.

Einstein on the Beach, considered unusual for its minimalist style and non-narrative structure when it first debuted in 1976, is a collaboration with theatre director Robert Wilson. Glass and Wilson have worked together, off and on, for 35 years. Their last time teaming up was in 1998's Monsters of Grace.

"We don't work together all the time, but the encounters we've had have been very productive for both of us  We wanted to do it one more time," Glass said in an interview Friday with Jian Ghomeshi, host of CBC's Q cultural affairs show.

"Also there are two generations of people who haven't heard it," Glass said of Einstein on the Beach, which hasn't been mounted in North America for 20 years. It is being presented June 8-10 in Toronto.

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Philip Glass says he still considers the music of Einstein on the Beach progressive, more than three decades after its debut. (Associated Press)

Glass still considers the opera progressive, if only because he feels the classical genre has become more traditional in the intervening years.

"What Bob and I did, we staked out a kind of an outer edge of what progressive music could be. I really thought that other people would follow in that direction, but we went all the way out to left field and there was nobody there but us," he said.

In 1976, the opera was so unconventional that even the Philip Glass Ensemble had difficulties playing it. In the interim, musicians have adapted to Glass's style.

"We've been getting better at it. When we did it in 1976, I can truly say it was out of our reach. I had written something that my ensemble had to really work at to play," he said.

In addition to Einstein on the Beach, Glass has scored In the Penal Colony and an opera based on the life of Galileo. He has created numerous compositions for his Philip Glass Ensemble. Although considered a classical composer, he has also crossed genres, working with artists like David Bowie, Allen Ginsberg and Twyla Tharp and creating film scores for titles such as The Thin Blue Line and The Hours.

Glass talked to Q about his early musical education, why eastern music was such a strong influence on his style and why he embraces repetition in his compositions.